The present invention generally relates to liquid removal apparatus and, more particularly, to duct wall water extractors for aircraft environmental control systems.
Entrained moisture in environmental control systems (ECS) is transported through the conditioned air ducting at various points in the system. If this entrained moisture is not captured and drained away it can cause excessive moisture in the cockpit and/or avionics bay.
A dual scavenging separator is described in U.S. Pat. No. 4,179,273. The disclosed separator comprises a conical feature with an external spiral blade that swirls water droplets and particulates to the enclosing duct wall where they are drained away through slots in the wall into an external sump. A limited number of slots in the cone provide a flow path for the cleaned air. Although the described separator may capture entrained moisture, the tortuous and limited flow path area induces a significant pressure drop penalty for the cleaned air flowing through the device. The pressure drop results in reduced ECS capacity and/or engine efficiency for some aircraft applications.
A liquid separator assembly is described in U.S. Pat. No. 4,769,050. The disclosed assembly comprises two tubes (inlet and outlet), which are crimped, closed, perforated and housed within a surrounding enclosure. The air flow enters one tube, exits through the perforations into the enclosing chamber, and reenters the second tube through its perforations. The water droplets are separated from the air flow in the enclosing chamber and drained away. Unfortunately, this assembly also induces a significant pressure drop penalty caused by its tortuous and limited flow path area.
A liquid/gas separation device that does not require the air flow to go through a reduced airflow path is described in U.S. Pat. No. 5,302,301. In the disclosed separator, the water laden air flow enters an enlarged chamber tangentially, inducing a centrifugal force which drives the water droplets to the chamber wall and subsequently drain to the bottom of the chamber and out through a drain tube. The dried air moves to the center of the chamber where it is directed through a filter element that removes particulates prior to the air being discharged from the device. Unfortunately, the filter element induces a significant pressure drop penalty on the dried air flow. Additionally, this device requires a chamber with a large volume to allow the separation to occur. For some aircraft applications, there is limited space for devices to capture the entrained water due to the close packing of hardware and the large volume chamber may not be suitable.
As can be seen, there is a need for a water separator device that does not require a volume expansion or settling chamber to separate the water from the air stream. Because the amount of ECS airflow is critical, a water extraction device that does not excessively restrict the airflow is needed. Further, a water extractor that has a smaller and more compact design is needed.